“You can see a change in the ecosystem overnight, specifically with hydrilla. You will see a normal pond and then at the end of the growing season it will be completely full of hydrilla,” said Nicole White, founder of Little Bear Environmental Consultingwhich often works with city and state departments to combat invasive species. “Nothing else can survive there. “He’s drowned.”
White, in partnership with other organizations, including the Department of Environmental Protection, worked to eradicate hydrilla in the Croton River from 2018 to 2022. Of the 449 sites they initially sampled, hydrilla was present at 40 percent of them.
In the end, they successfully eradicated hydrilla from three miles of river downstream using a very low concentration of herbicide over five seasons, but the impact of hydrilla on the river ecosystem was so severe that at the end of the project, White had to replant many native species. Aquatic plants in the Croton River.
According to Taylor, the hydrilla still remains in the New Croton Reservoir. The Department of Environmental Protection is also using herbicides to change that.
The presence of hydrilla in the reservoir may have implications not only for the marine ecosystem, but also for water quality and the survival of local birds. Hydrilla is also known to harbor cyanobacteria, which can become a toxin.Aetokthonos hydrillicola. This type of harmful algae can kill waterfowl and bald eagles, and has the potential to harm human health.
“It is a neurotoxin, so in places where Aetoctonos is found in the hydrilla, many wild animals have died from brain injuries,” White said. “So the fish have died, the reptiles have died, like the turtles, the water birds that eat the hydrilla, and then also the predators of those water birds.”
Climate change causes warmer weather in the fall and more extreme precipitation that moves sediment in the water column. This creates better conditions for the spread of hydrilla, the proliferation of cyanobacteria and, therefore, these toxins. Its presence has not been confirmed in New York state, although the Department of Environmental Protection is taking samples to detect it.
The water flea, an imminent threat
Last year the hook water flea was found in the reservoir. The novelty of its arrival means that Department of Environmental Protection officials have not yet seen any adverse impacts on the marine ecosystem and its broader implications for the food chain are unknown. The water flea can affect water quality by eating large amounts of zooplankton, creating better conditions for the growth of harmful algae. Taylor believes it was probably transferred through fishing gear because water flea eggs can survive drying out for long periods of time.
Like the zebra mussel, it is virtually impossible to completely eliminate water fleas from a body of water once they have become established. The most important thing for many scientists is often stopping its spread to new waterways: About 40 percent of New York’s fresh water is connected to canals, making it much easier for species to move.
